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Author: 


Vose,  George  Leonard 


Title: 

Bridge  disasters  in 
America 

Place: 

New  York 

Date: 

1880 


^^-^^\o>^  -g? 


MASTER   NEGATIVE   « 


COLUMBIA  UNIVERSITY  LIBRARIES 
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ORIGINAL  MATERIAL  AS  FILMED  •    EXISTING  BIBLIOGRAPHIC  RECORD 


•530.3 
V92 


Vose,  George  Leonard,  18S1- 

Bridge  disasters  in  Amerioat  the  cause  and 
the  remedy.  New  York,  The  Railroad  gatette, 
1880. 

30  p.     20om. 


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THE  LIBRARIES 


SCHOOL  OF  BUSINESS 


I 


BRIDGE      DISASTERS 


•       IN 


^MEKICA.: 


THE  CAUSE  AND  THE  REMEDY. 


BT  PROFESSOR  GEORGE  L.  VOSE. 


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3.B8d.  *      ■    *    I       -   " 
PUBLISHED  B\'   "ME  RA'LROAO   GAZETTE. 

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BRIDGE  DISASTERS  IN  AMERICA. 


THE    CAUSE    AJS^D    XHE    REJMEIDY. 

A  few  years  ago  an  iron  highway  bridge  at  Dixon,  111., 
fell,  while  a  crowd  was  npon  it,  and  killed  sixty  persons. 
The  briefest  inspection  of  t.  .t  bridge  by  any  competent  en- 
gineer would  have  been  sure  to  condemn  it.  A  few  years 
later  the  Ashtabula  bridge,  upon  the  Lake  Shore  Railroad, 
broke  down  under  a  passenger  train,  and  killed  from  80  to 
100  passengers.  The  report  of  the  committee  of  the  Ohio 
Legislatm-e  appointed  to  investigate  that  disaster  concluded, 
first,  that  the  bridge  went  down  under  an  ordinary  load  by 
reason  of  defects  in  its  original  construction  ;  and,  secondly, 
that  the  defects  in  the  original  construction  of  the  bridge 
could  have  been  discovered  at  any  time  after  its  erection  by 
careful  examination.  Hardly  had  the  public  recovered 
from  the  shock  of  this  terrible  disaster  when  the  Tariffville 
calamity  added  its  list  of  dead  and  wounded  to  the  long 
roll  already  charged  to  the  ignorance  and  recklessness  which 
characterizes  so  much  of  the  management  of  the  public 
works  ill  this  country. 

There  are  many  bridges  now  in  use  upon  our  railroads  in 
no  way  better  than  those  at  Ashtabula  and  Tariffville,  and 
which  await  only  the  right  combination  of  circumstances  to 
tumble  down.  There  are,  by  the  laws  of  chance,  just  so 
many  persons  who  are  going  to  be  killed  on  those  bridges. 
There  are  hundreds  of  highway  bridges  now  in  daily  use 
which  are  in  no  way  safer  than  the  bridge  at  Dixon  was, 
and  which  would  certainly  be  condemned  by  five  minutes  of 
competent  and  honest  inspection.  More  than  that,  many  of 
them  have  already  been  condemned,  as  unfit  for  public  use, 
but  yet  they  are  allowed  to  remain,  and  invite  the  disaster 
which  is  sure  to  come.  Can  nothing  be  done  to  prevent  this 
reckless  and  wicked  waste  of  human  life  ?  Can  we  not  have 
some  system  of  public  control  of  public  works  which  shall 
secure  the  public  safety «    The  answer  to  this  question  will 


"^MmK 


be,  not  until  the  public  is  a  good  deal  more  enlightened  upon 
these  mattei'8  than  it  is  now. 

It  has  been  very  correctly  remarked  that  in  order  to  bring 
a  disaster  to  the  public  notice  it  must  be  emphasized  by  loss 
of  life.     The  Ashtabula  bridge  fell  and  killed  over  80  per- 
sons, and  a  storm  of  indignation  swept  over  the  country 
from  one  end  to  the  other.    No  language  was  severe  enough 
to  apply  to  the  managers  of  the  Lake  Shore  Railroad;  but 
if  that  very  bridge  had  fallen  under  a  freight  train,  and  no 
one  had  been  injured,  the  occurrence  would  have  been  dis- 
missed with  a  paragraph,   if,   indeed,  it  had  received  even 
that  recognition.    In  February,  1879,  a  span   110  ft.  long 
of  an  iron  bridge  on  the  Chicago  &  Alton  Railroad,  at  Wil- 
mington, 111.,  fell  as  a  train  of  empty  coal  cars  was  passing 
over  it,  and  three  cars  were  precipitated  into  the  river,  a 
distance    of   over   30   ft..    No   one   was   injured.    Not  a 
word  of  comment  was  ever  made  in  regard  to  this  occur- 
rence.   Suppose   that    in   place   of   empty   coal    cars   the 
train  had  consisted  of  loaded  passenger  cars,  and  that  100 
persons  had  been  killed.      We  know  very  well  what  the 
result  would  have  been.    Is  not  the  company  just  as  much 
to  blame    in   one  case    as  in  the  other  ?    On  the  night  of 
the    9th    of    November     last    one    span    of    the     large 
bridge  over  the  Missouri  River,  at  St.  Charles,  upon  the  St. 
Louis,  Kansas  City  &  Northern  Railway,  gave  way  as  a 
freight  train  was  crossing  it,  and  17  loaded  stock  cars  and 
the  caboose  fell,  a  distance  ©f  80  ft.,  into  the  river.     Two 
brakemen  and  two  drovers,  who  were  in  the  caboose,  were 
killed.     The  bridge,  says  the  only  account  that  has  appeared, 
did  not  break,  apparently,  for  the  whole  span  went  down 
with  the  cars  upon  it    It  could  hardly  make  much  difference, 
we  should  suppose,  to  the  four  men  who  were  killed,  whether 
tiie  bridge  broke  down  or  went  down.   This  disaster  occurred 
early  last  November,  and  not  a  word  has  appeared  in  the 
papers  since  in  regard  to  it.      Suppose  that  in  place  of  17 
stock  cars  half-a-dozen  passenger  cars  had  fallen  from  a 
height  cf  80  ft.  into  the  river,  and  that  in  place  of  killing 
two  brakemen  and  two  drovers  two  or  three  hundred  pas- 
sengers had  been  killed.     Is  not  the  general  public  just  as 
concerned  in  one  case  as  the  ot^er  ? 

Suppose  that  a  bridge  now  standing  is  exactly  as  unsafe  as 
the  Ashtabula  bridge  was  the  day  before  it  felL  Would 
it  be  possible  to  awaken  public  attention  enough  to 
have  it  examined  ?     Probably  not.    A  short  time  since  the 


writer  endeavored  to  induce  one  of  the  leading  dailies  in 
Massachusetts  to  expose  a  wi*etchedly  unsafe  bridge  in  New 
England  ;  but  the  editor  declined  on  the  ground  that  the  mat- 
ter was  not  of  sufficient  interest  for  his  readers  ;  but  less 
than  a  month  afterward  he  devoted  three  columns  of  his  pa- 
per to  a  detailed  account  of  a  bridge  disaster  in  Scotland, 
and  asked  why  it  was  that  such  things  must  happen,  and  if 
there  was  no  way  of  determining  in  advance  whether  a 
bridge  was  safe  or  not.  This  editor  certainly  would  not 
maintain  that,  in  itself,  it  was  more  important  to  describe  a 
disaster  after  it  had  occurred,  than  to  endeavor  to  prevent 
the  occurrence  ;  but,  as  a  business  man,  he  knew  perfectly 
well  that  his  patrons  would  read  an  account  giving  all  of  the 
sickening  detail  of  a  terrible  catastrophe,  while  few,  if  any, 
would  wade  through  a  dry  discussion  of  the  means  for  pro- 
tecting the  public  from  just  such  disasters.  The  public  is  al- 
ways very  indignant  with  the  effect,  but  does  not  care  to 
trouble  itself  with  the  cause  ;  but  the  effect  never  will  be 
prevented  until  the  cause  is  controlled,  and  the  sooner  the 
public  understands  that  the  caiise  is  in  its  own  hands,  to  be 
controUed  or  not,  as  it  chooses,  the  sooner  we  shall  have  a 
remedy  for  the  fearful  disasters  which  are  altogether  too 
<K>mmon  in  the  United  States. 

In  a  country  where  government  controls  all  matters  on 
which  the  public  safety  depends,  and  where  no  bridge  over 
which  the  public  is  to  pass  is  allowed  to  be  built  except  after 
the  plans  have  been  approved  by  competent  authority,  where 
no  work  can  be  executed  except  under  the  rigid  inspection  of 
the  best  experts,  nor  opened  to  the  public  until  it  has  been 
officially  tested  and  accepted,  it  makes  little  or  no  difference 
whether  the  public  is  informed  or  not  upon  these  matters; 
but  in  a  coimtry  like  the  United  States,  where  any  man  may 
at  any  time  open  a  shop  for  the  manufacture  of  bridges, 
whether  he  knows  anything  about  the  business  or  not,  and  is 
at  liberty  to  use  cheap  and  insufficient  material,  and  where 
public  officers  are  always  to  be  found  ready  to  buy  such 
bridges  simply  because  the  first  cost  is  low,  and  to  place  them 
in  the  public  ways,  it  makes  a  good  deal  of 
difference.  There  is  at  present  in  this  country  absolutely 
no  law,  no  control,  no  inspection,  which  can  prevent  the 
building  and  the  use  of  unsafe  bridges  ;  and  there  never 
will  be  until  the  people  who  make  the  laws  see  the  need  of 
«uch  control.  There  is  no  one  thing  more  important  in  this 
matter  than  that  we  should  be  able  to  fix  precisely  the  re- 


sponabUity,  ,n  case  of  disaster,  upon  some  per»o„  to  whom 
the  proper  punishment  may  be  appUed.  l" even- mUwav 
Arector  ortown  or  county  officer,  knew  that  he  w™  he'd 
personally  accountable  for  the  failure  of  any  bnd«    n  2f 

structures^  If  we  could  show  that  a  certain  bridge  in  a  lar« 
town  had  been  tora  longtime,  old,  rotten, ,  om-outi^nd  li^ 

that  the  public  officers  having  charge  of  such  a  bridge  toew 
this  t»  be  the  case,  and  still  aUowed  the  public  to  pa^  ove^T 

a^d^Mv!^'n  f  '"""'"  ""•  *"»«8^  would  be  short 

and  decisive.    Once  let  a  town  have  heavy  damages  to  oav 
and  let  it  know  at  the  same  time  that  thTtowrofflcl„'^S 
clearly  accountable  for  the  loss,  and  it  is  Dossible  Tl.7.^ 
would  be  wiUing  to  adopt  some  system  tilt  T^d  ^^n 
the  recurrence  of  guch  an  outlay.  prevent 

To  see  what  may  be  accomplished  by  an  efficient  system 
regard  to  the  stinictures  to  oe  inspected.    We  have  now    i^ 

r.^ITrid.^''  T-'^y-botruponour^^'dTaTo.^ 
nuiroads,  bndges  made  entirely  of  iron,  bridges  of  wood  and 
mm  combmed,  and  occasionally,  though  noroften^w™ 
days,  a  bndge  entirely  of  wood;  and  thL  struck  .^  to 
be  seen  of  a  great  variety  of  patterns,  of  aU  siJTa^iu 
eveiT  Stage  of  pr^rvation.  America;  enginir^'e  ,i 
w^exceUed  in  this  branch  of  their  busing  Utoguns^-" 
P«»ed  by  any  other  m.tion.  Of  late  years,  so  ^at  hJC 
the  demand  for  bridge  work  that  this  brai^ch  o^ngin"  r^° 
h«  become  a  trade  by  itself,  and  we  Bnd  immenTToX 

^Zt^"  mUh'"  T'T  "™*y<"  ""«  "ostadm^iw; 
adapted     machine    tools,    devoted    exclusively    to     the 

matang  ^  bridges   „f    w«k.,    i„„.   steel,    or'  alf  cc^m! 

-thiss^al.Ttion'i'as  ^Trim^ive' 'X 'th:  ^^tt 
of  the  preduct,  to  lessen  the  c«t,  and  to  increase  the  de^^ 


of  these  wretched  traps  do  not  tumble  down,  and  cause  a 
greater  or  less  loss  of  life;  and  at  the  same  time,  with  unin- 
formed people,  throw  discredit  on  the  whole  modern  sys- 
tem of  bridge-building.  This  evil  affects  particularly 
highway  bridges.  The  ordinary  county  commissioner 
or  select-man  considers  himself  amply  competent  to 
contract  for  a  bridge  of  wood  or  iron,  though 
he  may  never  have  given  a  single  day  of  thought  to  the  mat- 
ter before  his  appointment  to  office.  The  result  is  that  we 
see  all  over  the  country  a  jjreat  number  of  highway  bridges 
which  have  been  sold  by  dishonest  builders  to  ignorant  offi- 
cials and  which  are  on  the  eve  of  falling,  and  await  only  an 
extra  large  crowd  of  people,  a  company  of  soldiers,  a  pro- 
cession, or  something  of  the  sort  to  break  down. 

After  a  defective  bridge  falls  it  is  in  nearly  every  case  easy 
to  see  why  it  did  so.  It  would  be  just  about  as  easy  to  tell 
in  advance  that  such  a  bridge  would  fall  if  it  ever  happened 
to  be  heavily  loaded.  Hundreds  of  highway  bridges  are  to- 
day standing  simply  because  they  never  happen  to  have  re- 
ceived the  load  which  is  at  any  time  liable  to  come  upon 
them. 

Not  many  years  ago  a  new  highway  bridge  of  iron  was 
to  be  made  over  a  broad  river  in  one  of  the  largest  towns  in 
New  England.  The  county  commissioners  desired  a  well- 
known  engineer,  especially  noted  as  a  bridge-builder,  to 
superintend  the  work,  in  order  to  see  that  it  was  properly 
executed.  The  engineer,  after  inspection  of  the  plans,  told 
the  commissioners  plainly  that  the  design  was  defective,  and 
would  not  make  a  safe  bridge  ;  and  that  unless  it  was 
materally  changed  he  would  have  nothing  to  do  with  it. 
The  bridge,  however,  was  a  cheap  one,  and  as  such  com 
mended  itself  to  the  commissioners,  who  proceeded  to  have 
it  erected  according  to  the  original  plan  ;  and  these  same 
commissioners  now  point  to  that  bridge,  which  has  not  yet 
fallen,  but  which  is  liable  to  do  so  at  any  time,  as  a  complete 
vindication  of  their  judgment,  so  called,  as  opposed  to  that 
of  the  engineer  who  had  spent  his  life  in  building  bridges. 

An  impression  exists  in  the  minds  of  many  persons  that 
an  iron  bridge  is  necessarily  a  strong  bridge.  This  is  a  great 
mistake.  There  are  good  iron  bridges  and  there  are  also  very 
poor  ones.  A  good  iron  bridge  is  the  best  bridge  one  can  buy ; 
but  a  poor  iron  bridge  is  the  worst — ^much  worse  than  a  poor 
wooden  one;  for  when  an  iron  bridge  falls  it  is  apt  to  go  all 
at  once,  but>  wooden  one  shows  signs  of  failure  long  before 


8 

it  actually  gives  way.  Another  fallacy  which  infests  8ome 
persons  is  the  notion  that  it  is  purely  a  matter  of  opinion 
whether  a  bridge  is  safe  or  not.  In  nine  cases  out  of  ten  it 
IS  not  at  all  a  matter  of  opinion,  but  a  matter  of  fact  and 
of  arithmetic.  The  whole  question  always  comes  to  this: 
Is  the  material  in  this  bridge  of  good  quality,  is  there 
enough  of  It,  is  it  property  put  together  ?  With  given  di- 
mensions, and  knowing  the  load  to  be  carried,  it  is  a  matter 
of  the  very  simplest  computation  to  fix  the  size  of  each 
member.  We  know  what  one  square  inch  of  iron  will  hold 
and  we  also  know  total  the  number  of  pounds  to  be  sustained- 
and  It  IS  no  matter  of  opinion,  but  one  of  simple  division,  aJ 
to  how  many  times  one  will  go  into  the  other. 

But,  it  may  be  asked,  can  the  precise  load  which  is  coming 
upon  any  structure  be  exactly  fixed  ?    Are  not  the  circum- 
stances under  which  bridges  are   loaded    very  different  ? 
Bridges  in  different  localities  are  certainly  subjected  to  very 
different  loads,  and  under  very  different  conditions;  never- 
theless, the  loads  to  be  provided  for  have  been  fixed  by  the 
best  authority  for  all  cases,  within  narrow  enough  limits  for 
all  practical  purposes.    Few  persons  are  aware  of  the  weight 
of  a  closely  packed  crowd  of  people.     Mr.   Stoney,  one  of 
the  best  authorities,  packed  30  persons  upon  an  area  of  29,% 
square  feet,  and  at  another  time  he  placed  58  persons  upon 
an  area  of    57  square   feet.    In   the    first   case,    the    re- 
sult   was    a    load    of     149    lbs.    per    square    foot,    and 
m    the    second     case    a    load    of     147,*,    lbs.    per    foot 
Such  cramming,"  says  Mr.  Stoney,  "  could  scarcely  occur 
in  Dractice,  except  in  portions  of  a  strongly  excited  crowd- 
but  I  have  no  doubt  that  it  does  occasionally  so  occur." 
"  In  my  own  practice,"  be  continues,  "  I  adopt  100  lbs.  p^r 
square  foot  as  the  standard  working  lead,  distributed  uni- 
formly over  the  whole  surface  of  a  public  bridge,  and  140 
lbs.  per  square  foot  for  certain  portions  of  the  structure- 
such  for  example  as  the  foot-paths  of  a  bridge  crossings 
navigable  river  in  a  city,  which  are  liable  to  be  severely 
tried  by  an  excited  crowd  during  a  boat-race,  or  some  simi- 
lar occasion."  Tredgold  and  Rankine  estimate   the  weight  of 
a  dense  crowd  at  180  lbs.  per  square  foot.      Mr.  Brunei  used 
100  lbs.  m  his  calculations  for  the  Hungerford  Suspension 
Bridge.    Mr.  Drewry,  an  old  but  exceUent  authority,  ob- 
serves "that  any  body  of  men  marching  in  step  at  from  3 
to  3K  miles  an  hour  wiU  strain  a  bridge  at  least  as  much  as 
double  the  same  weight  at  rest;"  and  he  adds:  "  In  prudence 


9 

not  more  than  one-sixth  the  number  of  infantry  that  would 
fill  a  bridge  should  be  permitted  to  march  over  it  in  step." 
Mr.  Roebling  says,  in  speaking  of  Niagara  Falls  Railroad 
Suspension  Bridge:  '*  In  my  opinion,  a  heavy  train,  i-unning 
at  a  speed  of  twenty  miles  an  hour,  does  less  injury  to  the 
structure  than  is  caused  by  twenty  heavy  cattle  under  full 
trot.  Public  processions,  marching  to  the  sound  of  music,  or 
bodies  of  soldiers  keeping  regular  step,  will  produce  a  still 
more  injurious  effect." 

Evidently  a  difference  should  be  made  in  determining  the 
load  for  London  Bridge  and  the  load  for  a  highway  bridge 
upon  a  New  England  country  road  in  a  thinly  settled  district. 
A  bridge  that  is  strong  enough  is  just  as  good  and  just  as 
safe  as  one  that  is  ten  times  stronger,  pnd  even  better;  for 
in  a  large  bridge,  if  we  make  it  too  strong,  we  make  it  at  the 
same  time  too  heavy.  The  weight  of  the  structure  itself  has 
to  be  sustained,  and  this  part  of  the  load  is  a  perpetual  drag 
on  the  material.  In  1875,  the  American  Society  of  Civil 
Engineers,  in  view  of  the  repeated  bridge  disastei*s  in  this 
country,  appointed  a  committee  to  report  upon  "  The  Means 
of  Averting  Bridge  Accidents."  We  might  expect,  when  a 
society  composed  of  some  hundreds  of  our  best  engineers 
selects  an  expert  conmiittee  of  half  a  dozen  men,  that  the 
best  authority  would  be  pretty  well  represented,  and  such 
was  eminently  the  case.  It  would  be  impossible  to  have 
combined  a  greater  amoimt  of  acknowledged  talent,  both 
theoretical  and  practical,  with  a  wider  and  more  valuable 
experience,  than  this  committee  possessed.  The  first  point 
taken  up  in  the  report  is  the  determination  of  the  loads  for 
which  both  railroad  and  highway  bridges  should  be  propor- 
tioned. In  regard  to  highway  bridges,  a  majority  of  the 
coDunittee  reported  that  for  such  structures  the  standard 
loads  should  not  be  less  than  as  shown  in  the  following 
table: 

^Pounds  per  Square  foot.— v 
Span.  Class  A.      Class  B.  Class  C. 

00ft.  and  leM 100  100  70 

eoto  100ft 90  76  60 

100  to  200  ft... » 75  aO  50 

200to400ft eO  80  40 

Class  A  includes  city  and  suburban  bridges,  and  those  over 
large  rivers  where  great  concentration  of  weight  is  possible ; 
Class  B  denotes  higbway  bridges  in  manufacturing  districts, 
having  well  ballasted  roads;  and  Class  C  refers  to  ordinary 
country  road  bridges,  where  travel  is  less  frequent  and 
lighter.    A  minority  of  the  committee  modified  the  table 


10 

above  by  putting  all  highway  bridges  into  the  first  class 
and  by  making  the  loads   larger  by  a  smaU  amount.     The 
whole  committee  agreed  in  making  the  load  per  square  foot 
less  as  the  span  is  greater,  which  is  of  course  correct.    It 
would  seem  eminently  correct  to  make  a  difference  between 
a  bridge  which  carries  the  continuous  and  heavy  traffic  of  a 
large  city  and  one  which  is  subjected  only  to  the  compara- 
tively hght  and  infrequent  traffic  of  a  country  road.  At  the 
same  time  it  should  not  be  forgotten  that  in  a  large  part  of 
the  Umted  States  a  bridge  may  be  loaded  by  ten,  twenty  or 
even  thirty  lbs.  per  square  foot  by  snow  and  ice  alone,  and 
that  the  very  bridges  which  from  their  location  we  should  be 
apt  to  make  the  lightest  are  those  which   would  be  most 
iikely  to  be  neglected,   and   not   relieved  from   a   heavy 
accumulation  of  snow.    In  view  of  the  above,  and  remem- 
bering that  a  moving  load  produces  a  much  greater  strain 
upon  a  bridge  than  one  which  is  at  rest,  we  may  be  sure 
that,  as  the  committee  above  referred  to  recommend,  the 
loads  should  not  be  less  than  those  given  in  the  table.    We 
can  easily  see  that  in  special  cases  they  should  be  more. 

There  is  another  point  in  regard  to  the  loading  of  a  high- 
way bndge  which  is  to  be  considered.    It  often  happens 
that  a  very  heavy  load  is  carried  over  such  bridges  upon  a 
single  truck,  thus  throwing  a  heavy  and  concentrated  load 
upon  each  point  as  it  passes.    Mr.  Stoney  states  that  a  wagon 
with  a  crank  shaft  of  the  British  ship  Hercules,  weighing 
about  45  tons,  was  refused  a  passage  over  Westminster  iron 
bndge,  for  fear  of  damage  to  the  structure,  and  had  to  be 
earned  over  the  Waterioo  Bridge,  which  was  of  stone,  and 
he  says  that  m  many  cases  large  boilers,  heavy  forgiugs  or 
castings,  reach  as  high  as  12  tons  upon  a  single  wheel.    The 
report  of  the  American  Society  of  Engineers,  above  referred 
to,  advises  that  the  floor  system  be  strong  enough  to  can-y 
the  following  loads  upon  four  wheels:  on  Class  A,  24  tons; 
Uass  B,  16  tons,  and  Class  C,  8  tons;  though  it  is  stated  that 
these  do  not  include  the  extraordinary  loads  sometimes  taken 
over  highways.     -  This  provision  for  local  loads,"  says  Mr. 
iioller,  one  of  the  committee,  "  may  seem  extreme,  but  the 
jar  and  jolt  of  heavy  springless  loads  conies  directly  on  all 
parts  of  the  flooring  at  successive  intervals,  and  admonishes 
us  that  any  errors  should  be  on  the  safe  side." 

To  pass  now  to  raiht)ad  bridges,  we  find  here  a  very  heavy 
load  coming  upon  the  structure  in  a  sudden  and  often  very 
violent  manner.    Experiment  and  observation  both  indicate 


11 

that  a  rapidly-moving  load  produces  an  effect  equal  to 
double  the  same  load  at  rest.  This  effect  is  seen  much  more 
upon  short  bridges,  where  the  moving  load  is  large  in  pro- 
portion to  the  weight  of  the  bridge,  than  upon  long  spans, 
where  the  weight  of  the  bridge  itself  is  considerable.  The 
actual  load  upon  a  short  bridge  is  also  more  per  foot  than 
upon  a  long  one,  because  the  locomotive,  which  is  much 
heavier  than  an  equal  length  of  cars,  may  cover  the  whole 
of  a  short  span,  but  only  a  part  of  a  longer  one.  The  largest 
engines  in  use  upon  our  railroads  weigh  from  75,000  to 
80,000  lbs.  on  a  wheel-base  not  over  12  ft.  in  length,  or 
2,800  lbs.  per  foot  for  the  whole  length  of  the  engine,  and 
from  20,000  to  24,000  lbs.  on  a  single  pair  of  wheels.  The 
heaviest  coal  trains  will  sometimes  weigh  nearly  a  ton  per 
lineal  foot,  the  oi'dinar}' freight  trains  from  1,600  to  1,800 
lbs.,  and  passenger  trains  from  1,000  to  1,200  lbs.  per  foot. 
Any  bridge  is  liable  to  be  traversed  by  two  heavy 
freight  engines,  followed  by  a  load  of  a  ton  to  the  foot,  so 
that  if  we  proportion  a  bridge  for  3,000  lbs.  per  foot,  for  the 
total  engine  length,  and  for  a  ton  per  foot  for  the  rest  of  the 
bridge,  bearing  in  mind  that  80,000  lbs.  may  come  upon  any 
12  ft.  of  the  track,  and  that  any  one  point  may  be  called 
upon  to  sustain  24,000  lbs.,  and  regarding  the  increase  of 
strain  on  short  spans  due  to  high  speeds,  we  have  the  follow- 
ing loads  for  different  spans,  exclusive  of  the  weight  of  ^he 
bridge : 

Span.                       Lbs.  per  foot.    Span.  Lbs.  per  foot. 

12 7,000  50 3,000 

15 6.000         I  100 ;j,800 

20 4,800  200 2,600 

25. 4,000     300 2,500 

30 3,600    t  400 2,450 

40., 3,200         !500 2,400 

The  above  does  not  vary  essentially  from  the  English 
practice,  and  is  substantially  the  same  as  given  by  the  Com- 
mittee of  the  American  Society  of  Civil  Engineers. 

The  load  which  any  bridge  will  be  required  to  carry  being 
determined,  and  the  general  plan  and  dimensions  fixed,  the 
several  strains  upon  the  different  members  follow  by  a  sim- 
ple process  of  arithmetic,  leaving  to  be  determined  the  actual 
dimensions  of  the  various  parts  ;  a  matter  which  depends 
upon  the  power  of  different  kinds  of  material  to  resist  differ- 
ent strains.  This  brings  us  to  the  exceedingly  important 
subject  of  the  nature  and  strength  of  materials. 

It  has  been  said  that  we  know  what  one  square  inch  of  iron 
will  hold.    Like  the  question  of  loads,  above  examined,  this 


f  '■ 


■■■Ml 


l'':i 


12 

is  a  matter  which  has  been  settled,  at  any  rate  wlthhi  very 
narrow  limits,  by  the  experience  of  years  of  both  European 
and  American  engineers.     A  bar  of  the  best  wrou^ht-iron, 
one  inch  square,  will  not  break  under  a  tensile  strain  of  less 
than  60,000  lbs.    Only  a  smaU  part  of  this,  however,  is  to 
be  used  in  practice.     A  bar  or  beam  may  be  loaded  with  a 
greater  weight,  applied  as  a  permanent  or  dead  load,  than 
would  be  safe  as  a  moving  or  roUing  weight    A  load  may 
be  brought  upon  any  material  in  an  easy  and  gradual  man- 
ner so  as  not  to  damage  it,  while   the  same  load  could 
not  be  suddenly  and    violently  applied    without   injury 
The  margin  for  safety  should  be  greater  with  a  material  lia- 
ble to  contain  hidden  defects  than  with  one  which  is  not  so: 
and  it  should  be  greater  for  any  member  of  a  bridge  which 
is  subjected  to  several  different  kinds  of  strain  than  for  one 
which  has  to  resist  only  a  single-  form  of  strain.    Respect 
also  should  be  had  to  the  frequency  with  which  any  part  is 
subjected  to  strain  from  a  moving  load,  as  this  will  mani- 
festly influence  its  power  of  endurance.    The  rule  in  struc- 
tures having  so  important  an  office  to  perform  as  raih-oad  or 
highway  bridges,   should  be,  in  all  cases,  absolute  safety 
under  all  conditions. 

The  British  Board  of  Tn»de  fixes  the  greatest  strain  that 
shaU  come  upon  the  material  in  a  wrought-iron  bridge  from 
the  combined  weight  of  the  bridge  and  load,  at  5  tons  per 
square  mch  of  the  net  section  of  the  metal.     The  French 
practice  allows  3^,  tons  per  square  inch  of  the  gross  section 
of  the  metal,  which,  considering  the  amount  taken  out  by 
nvet  holes,  is  substantially  the  same  as  the  English  allow- 
ance.   The  report  of  the  American  Society  above  referred 
to  recommends  10,000  lbs.  per  inch  as  the  maximum  for 
wrought-iron  in  tension  in  raili-oad  bridges.    For  highway 
bridges,  which  are  not  subjected  to  such  severe  treatment 
a  unit  strain  of  15,000  lbs.  per  square  inch  is  often  allowed.' 
A  very  common  clause  in  a  specification  is  that  The  Factor  of 
S  ifety  shaU  be  four,  fi  veor  six,as  the  case  may  be,  meaning  by 
this  that  the  actual  load  shall  not  exceed  one  fourth,  one-fifth 
or  one-sixth  part  of  the  breaking  load.    It  is  a  little  unfor- 
tunate that  this  term,  "factor  of  safety,"  has  found  its  way 
mto  use  just  as  it  has,  for  it  by  no  means  indicates  what  is 
mtended,  or  what  it  is  supposed  to.    The   true  margin  for 
safety  is  not  the  difference  between  the  working  strain  and 
the  breaking  strain,  but  between  the  working  strain  and  that 
strain  which  will  in  any  way  unfit  the  material  for  use.  Now 


18 

any  material  is  unfitted  for  use  when  it  is  so  far  distorted  by 
overstraining  that  it  cannot  recover,  or,  technically 
speaking,  when  its  elastic  limit  has  been  exceeded. 
The  elastic  limit  of  the  best  grades  of  iron  is  just  about 
one-half  the  breaking  weight,  or  from  85,000  to  30,000  lbs. 
per  square  inch ;  so  that  the  working  strain  of  10,000  lbs.  per 
inch  gives  a  factor  of  safety  of  two  and  a  half  or  three,  in- 
stead of  six.  If  the  ratio  between  the  elastic  limit  and  the 
breaking  weight,  t.  e.,  if  the  quality  of  the  iron  was  always 
the  same,  it  might  make  no  great  difference  how  we  used  our 
factor ;  but  some  iron  is  hard  and  brittle,  while  other  iron  is 
soft  and  ductile.  A  high  breaking  strength  may  be  due  to 
the  toufi:hness  of  the  iron,  or  to  the  hardness  of  the  iron.  A 
soft  and  ductile  iron  will  stretch  more  or  less  before  bteak- 
ing,  while  a  hard  iron  will  often  snap  short 
off  without  warning,  and  at  the  same  time 
both  may  have  the  same  breaking  strength.  A  tough 
and  ductile  iron  should  bend  double  when  cold  without  show- 
ing any  signs  of  fracture,  and  should  stretch  15  per  cent,  of 
its  length  before  breaking ;  but  much  of  the  iron  used  in 
bridges,  although  it  may  hold  50,000  lbs.  per  inch  before 
failing,  will  not  bend  over  90  degrees  without  cracking,  and 
has  an  elastic  limit  as  low  as  18,000  lbs.  It  is  thus  full  as 
important  to  specify  that  an  iron  should  have  a  high  elastic 
limit,  as  that  it  should  have  a  high  breaking  weight.  A 
specification  therefore  which  allowed  no  material  to  be 
strained  by  more  than  10,000  lbs.  per  inch,  and  no  iron  to 
be  used  with  a  less  elastic  limit  than  25,000  lbs.,  would  at 
the  same  time  agree  with  the  standard  requirement  both  in 
England  and  in  the  United  States,  and  would  also  secure  a 
good  quality  of  iron. 

The  writer  has  before  him  two  documents  which  illustrate 
the  preceding  remarks.  The  first  Is  the  account  of  the  tests 
of  the  iron  which  came  from  the  Tariffville  bridge  after  its 
failure,  and  the  second  is  the  specification  for  the  bridges 
upon  the  Cincinnati  Southern  Railway.  The  Tariffville 
bridge,  though  nominally  a  wooden  one,  like  most  structures 
of  the  kind  relied  entirely  upon  iron  rods  to  keep  the 
woodwork  together.  Though  the  rods  were  too  small, 
and  seriously  defective  in  manufacture,  the  bridge  ought 
not  to  have  fallen  from  that  cause.  The  ultimate  strength 
of  the  iron  was  not  what  it  should  have  been,  but  yet  it  was 
not  low  enough  to  explain  the  disaster;  but  when  we  look  at 
the  quality  of  the  iron  we  have  the  cause  of  the  fall.    The 


.-5*5  IP 


■■■i 


14 

rods  taken  from  the  bridge  show  an  ultimate  tensile  strength 
per  square  inch  of  47,5t50  lbs.,  but  an  elastic  limit  of  only 
19,000  lbs.,  while  the  strain  which  was  at  any  time  liable  to 
come  upon  them  was  23,000  lbs.  per  square  inch,  or  3,000 
lbs.  more  than  the  elastic  hmit.  The  fracture  of  the  tested 
rods,  which  it  is  stated  broke  with  a  single  blow  of  the  ham- 
mer very  much  in  the  manner  of  cast-iron,  show  a  very  in- 
ferior quality  of  material.  The  rods  broke  in  the  bridge  ex- 
actly where  we  should  look  for  the  faUure,  viz.  in  the 
screw,  at  the  end.  No  ordinary  inspection  wonld  have  de- 
tected this  weakness.  No  inspection  did  detect  it;  but  a 
proper  specification,  faith  fuUy  carried  out,  woiUd  have  pre- 
vented the  disaster. 

Look  now  at  an  extract  from  the  specification  for  bridges 
upon  the  Cincinnati  Southern  Railway  : 

*'  AH  parts  of  the  bridges  and  trestle-works  must  be  nro- 
x)rtioned  to  sustain  the  passage  of  the  following  rolling 
oad,  a^  a  speed  of  not  less  than  30  miles  an  hour,  viz  :  two 
ocomotives,  coupled,  each  weighing  36  tons  on  the  drivers 
ma  space  of  12  feet,  the  total  weight  of  each  engine  and 
tender  loaded  being  66  tons  in  a  sjmce  of  50  feet,  and  fol- 
J^^  ?^'  loaded  cars  weighing  20  tons  each  in  a  space 
of  22  feet.      An  addition  of  25  per  cent,    will    be  made 
to   the  strains    produced    by  the   rolling   load    considered 
as   static,    m    all   i>arts    which    are    liable    to   be    thrown 
suddenly    under    strain    by    the    passage    of    a    rapidly 
moving   load.      A  similar  addition  of   50   per   cent.    wiU 
be  made  to  the  strain  on  suspension  links  and  riveted  con- 
nections of  stringers  with  floor-beams,  and  flooi-beams  with 
trusses.     The  iron-work  shall  be  so  profwrtioned  that  the 
weight  of  the  structure,  together  with  the  above  specified 
rollmg  load,  shall  in  no  part  cause  a  tensile  strain  of  more 
than  10,000  lbs.   per  square   inch  of  sectional  area.     Iron 
used  under  tensile  strain,  shall  be  tough,  ductile,  of  uniform 
quality,  and  capable  of  sustaining  not  less  than  50,000  lbs 
per  square    inch  of  sectional   area  without   fracture,  and 
25,000  lbs.  per  square  inch  without  taking  a  permanent  set. 
The  reduction  of  area  at  the  breaking  point  shall  average 
25  per  cent.,  and  the  elongation  15  j)er  cent.     When  cold 
the  iron  must  bend,  without  sign  of  fracture,  from  90  to  180 
degrees." 

A  specification  like  the  above,  properl}-  carried  out,  would 
put  an  absolute  stop  to  the  building  of  puch  structures  as 
the  Tariffville  bridge,  and  would  prevent  a  very  large  part 
of  the  catastrophies  which  so  often  shock  the  community, 
and  shake  the  public  faith  in  iron  bridges.  We  have 
referred  above  to  the  factors  of  safety  for  wrought-iron 
under  tension  only.  Similar  factors  have  been  determined 
for  other  kinds  of  materials,  and  for  other  kinds  of  strain. 


15 

The  preceding  remarks  in  regard  to  the  loads  for  which 
bridges  should  be  designed,  and  the  safe  weight  to  be  put 
upon  the  material,  are  given  to  show  how  far  the  safety  of  a 
given  bridge  is  a  matter  of  fact,  and  how  far  a  matter  of 
opinion.  It  will  be  seen  that  the  limits  within  which  we  are 
at  liberty  to  vary  are  quite  narrow  ;  so  that  bridge-building 
may  correctly  be  caUed  an  exact  science,  and  there  is  no  ex- 
cuse for  the  person  who  guesses  either  at  the  load  which  a 
bridge  should  be  deagued  to  bear  or  at  the  size  of  the  dif- 
ferent membei-s  of  the  structure.  Still  less  can  we  excuse 
the  man  who  not  only  guesses,  but  who,  in  order  to  build 
cheaply,  persistently  guess  on  the  wrong  side. 

We  often  hear  it  argued  that  a  bridge  must  be  safe  since 
it  has  been  submitted  to  a  heavy  load  and  did  not  break 
down.  Such  a  test  means  absolutely  nothing.  It  does  not 
even  show  that  the  bridge  will  bear  the  same  load  again; 
much  less  does  it  show  that  it  has  the  proper  margin  for 
safety.  It  simply  shows  that  it  did  not  break  down  at  that 
time.  Every  rotten,  worn-out  and  defective  bridge  that 
ever  fell  has  been  submitted  to  exactly  that  test.  More  than 
this,  it  has  repeatedly  happened  that  a  heavy  train  has  passed 
over  a  bridge  in  apparent  safety,  while  a  much  lighter  one 
passing  directly  afterward  has  gone  directly  through.  In  all 
such  cases  the  structure  has  been  weak  and  defective,  and 
finally  some  heavy  load  i>asses  over  and  cripples  the  bridge, 
so  that  the  next  load  produces  a  disaster. 

It  is  very  common  upon  the  completion  of  a  bridge  to  do 
what  is  termed  testing  it.  The  common  practice  in  England 
is  to  load  each  track  with  as  many  engines  and  tenders  as 
the  bridge  will  hold,  and  to  measure  the  corresponding  de- 
flection. The  proof-load  varies  from  one  and  a  half  tons  per 
foot  on  the  shorter  bridges  to  one  ton  per  foot  upon  longer 
ones-  but  when  the  span  exceeds  150  ft.  in  length  the  load  is 
made  somewhat  less.  In  France,  the  government  rules  for 
testing  wrought-iron  railway  bridges  are  as  follows:  Bridges 
under  66  ft.  span  are  loaded  with  a  dead  load  of  one  and  a 
half  tons  per  running  foot,  while  bridges  over  66  ft.  span 
are  loaded  with  1  i^  tons  per  foot.  Besides  the  above  proof,  by 
dead  weight,  a  train  composed  of  two  engines,  each  with  its 
tender  weighing  at  least  60  tons,  and  wagons  each  loaded 
with  12  tons,  in  suflicient  number  to  cover  one  span,  are  run 
over  the  bridge  at  speeds  from  12  to  22  miles  an  hour.  A 
second  trial  is  made  with  speeds  from  25  to  43  miles  an 
hour,  with  two  engines,  each  with  its  tender  weighing  35 


if 


I  !} 


16 

tons,  and  wagons  as  in  ordinary  passenger  trains,  enough  to 
cover  one  span.  On  double-track  bridges  two  trains  are 
made  to  cross,  at  first  in  parallel  and  then  in  opposite  di- 
rections, so  that  the  trains  may  meet  at  the  centre. 

Owing  to  the  lack  of  any  public  supervision  in  the  United 
States,  no  general  method  for  testing  either  railroad   or 
highway  bridges  exists.    In  some  cases  it  is  done,   in  some 
cases  it  is  not.    Bridges  made  by  our  first-class  firms,  under 
the  direction  of  engineers,  are  tested  in  substantially  the 
same  manner  as  in  Europe;  but  upon  many  of  our  smaller 
railroads,  which  cannot  afford  to  keep  an  engineer,  and 
generally  in  the  case  of  highway  bridges,  no  test  is  made  in 
many     instances     for     very     obvious    reasons.     In    one 
case    of   wretchedly    cheap  and    unsafe    highway   bridge 
which  came  recently  under  the  writer's  notice,  the  county 
commissioners,  in  order  to  quiet  an  impression  which  had 
arisen  that  the  bridge  was  not  altogether  sound,  tested  a 
span  122  ft.  long  with  a  load  estimated  to  weigh  58,600 lbs., 
or  480  lbs.  per  running  foot,  for  a  double  roadway.   The  com- 
missioners remarked  that  they  considered  this  a  satisfactory 
test,  as  it  was  not  propable  that  a  greater  weight  than  thia 
would  ever  be  applied  to  the  bridge  ;  and  added  that  the  test 
was  made  merely  to  satisfy  the  public  that  the  bridge  was 
abundantly  safe  for  all  practical  uses.    The  public  would, 
no  doubt,  have  been  satisfied  that  the  Ashtabula    bridge 
was  abundantly  safe  for  all  practical  uses  had  it  stood  on 
that  bridge  in  the  morning  and  seen  a  heavy  freight  train 
go  over  it ;  and  yet  that  very  bridge  broke  down  directly 
afterwai-d  under  a  passenger  train.     Now,  according  to  the 
common  notion  that  was  a  good  bridge  in  the  morning,  and 
a  very  bad  bridge,  or  rather  no  bridge  at  all,  in  the  evening. 
The  question  for  the  public  is— When  did  it  cease  to  be  a 
good  bridge  and  begin  to  be  a  bad  one  i    A  test  like  the  one 
referred  to  above  can  do  no  more  than  illustrate  the  ignor- 
ance or  lack  of  honesty  of  those  who  make  it,  or  those  who 
are  satisfied  with  it.    Such  a  test  might  come  within  a  dozen 
pounds  of  breaking  the  bridge  down  and  no  one  would  be 
the  wiser. 

For  the  test  of  a  bridge  to  be  in  any  way  satisfactory,  we 
must  know  just  what  effect  such  test  has  had  upon  the  struc- 
ture. We  do  not  find  this  out  by  simply  standing  near  and 
noting  that  the  bridge  did  not  break  down.  We  must,  in 
the  first  place,  compute  the  strains  which  the  load  throws 
upon  ea«h  pait  of  the  bridge,  and  see  that  no  member  i» 


17 

over-strained.    We  must  next  measure  precisely  the  amount 
by  which  the  bridge  is  depressed  under  the  load,  and  also 
how  far  the  work  recovers  from  such  depression  when  the 
load  is  removed.    A  locomotive,  when  first  run  on   to   a 
bridge,  will  produce  a  certain  depression— first,  by  the  clos- 
ing    up     and      stretching      of      the     joints,     and     sec- 
ondly     by      the       elongation       and       compression      of 
the  material.    If  the  load  is  left  on  for  a  considerable  time 
the  depression  wUl  be  seen  to  have  slightly  increased;  but 
after  a  longer  time  it  will  cease,  the  bridge  having  adapted 
itself  to  the  new  conditions  impresssd  upon   it.      When  the 
load  is  removed,  the  work  will  recover  its  first  position,  less 
a  small  amount,  termed  the  permanent  set.      So  long  as  the 
load  is  kept  within  the  proper  limits  this  permanent  set  is 
not  increased  by  any  number  of  subsequent  applications  of 
the  force  that  produced  it,  and  no  harm  is  done;   but   when 
the  load  is  so  great  that  each  application   of    the   force   in- 
creases the  set,  we  have  passed  the  elastic  limit,  and  failure 
is  only  a  question  of  time.  It  is  important  therefore  to  put  the 
load  on  a  second  time,  and  to  be  sure  that  the  bridge  does 
not  go  below  the  point  reached  at  first.    In  some  cases  a 
second  application  of  the  load  has  appeared  to  increase  the 
permanent  depression  ;  but  it  is  quite  likely  that  in  such  in- 
stances the  time  during  which  the  load  was  applied  at  first 
was  too  short  for  the  full  effect  to  show  itself.     Ample  time, 
too,  should  be  allowed  for  the  material  to  recover  after  the 
removal  of  the  load.    Mr.   Stoney  states  that  the  set  of 
wrought-iron  relaxes  to  a  considerable  extent,  even  after  the 
lapse  of  several  days  after  the  load  has  been  removed. 

In  view  of  the  preceding,  what  shall  we  say  of  a  bridge 
company  that  deliberately  builds  a  bridge  in  the  middle  of  a 
large  town,  where  it  will  be  subjected  to  heavy  teaming,  and, 
owing  to  its  peculiar  location,  to  heavy  crowds,  and  war- 
rants to  the  town  that  it  shall  hold  a  ton  to  the  running  foot, 
when  the  very  simplest  computation  shows  beyond  any 
chance  of  dispute  that  such  a  load  will  strain  the  iron  to 
40,000  lbs.  per  square  inch  ?  We  are  to  say  either  that  such 
a  company  is  so  ignorant  that  it  does  not  know  the  differ- 
ence between  a  good  bridge  and  a  bad  one,  or  else  so  wicked 
as  to  knowingly  subject  the  public  to  a  wretchedly  unsafe 

bridge. 

The  case  referred  to  is  not  an  imaginary  one,  but  exists 
to-day  in  the  main  street  of  a  large  New  England  town.  The 
jointsinthatbridge  which  will  safely  hold  but  20,000  lbs. 


T8 

wiU  be  required  to  hold  60,000  Ibe.  imder  a  load  of  one  ton 
per  lineal  foot,  which  the  builders  have  warranted  the 
bridge  to  carry  safely.  The  case  was  so  bad  that  after  a 
lengthy  controversy  the  town  officers  called  a  commission^ 
and  had  a  thorough  expert  examination  of  the  bridge.  The 
commission  reported  as  follows:  first,  *'The  bridge  in  its 
present  condition  might  carry  with  tolerable  safety  the 
ordinary  daily  traffic  to  which  it  is  now  subjected ;"  second,. 
"  If  a  span  of  this  bridge  should  at  any  time  be  subjected  to 
a  closely  packed  mass  of  people  on  the  draw-bridge,  or  a 
loosely  packed  crowd  on  top  of  a  heavy  accumulation  of 
ice  or  snow,  it  would  in  either  of  these  cases  be  in  imminent 
danger  of  falling,  and  would  be  so  over-strained  as  to  unfit 
it  for  even  moderate  service;"  thinj,  "If  the  span  should 
have  a  heavy  accumulation  of  ice  or  snow  on  it,  and  in  that 
condition  be  subjected  to  a  close-packed  mass  of  people,  it 
would  certainly  fall."  The  commission  further  reported 
that  the  bridge  at  one  place  had  a  factor  of  safety  of  only 
1  ,y^  ;  and  as  this  factor  refers  to  the  breaking  weight,  and 
not  to  the  elastic  limit,  the  real  factor  would  be  about  one- 
half;  or,  in  other  words,  half  the  load  which  is  at  any 
time  liable  to  come  upon  the  bridge  will  strain  it  beyond 
the  elastic  limit,  while  1  Vrib  times  the  load  will  break  it 
down. 

Not\vitbstanding  all  this,  and  in  the  face  of  this  report, 
the  president  of  the  bridge  company,  came  out  with  the 
statement  in  the  papers  that  he  "pronounced  the  bridge  per- 
fectly safe."  Thus  we  actuaUy  have  the  president  of  a 
bridge  company  in  this  country  stating  plainly  that  a  factor 
of  It',5^,  referred  to  the  breaking  weight,  makes  a  bridge 
"  perfectly  safe  ;"  for  he  very  wisely  made  not  the  slightest 
attempt  to  disprove  any  of  the  conclusions  of  the  commission  ; 
and  this  company  has  built  hundreds  of  highwav  bridges  all 
over  the  United  States,  and  is  building  them  to-day  where- 
ever  it  can  find  town  or  county  officers  ignorant  enough  or 
wicked  enough  to  buy  them. 

It  might  be  supposed  that  under  the  above  condemnation 
the  authorities  controlling  the  bridge  would  have  taken 
some  steps  to  prevent  the  coming  disaster.  They  did,  how- 
ever, nothing  of  the  kind  ;  but  allowed  the  public  to  travel 
over  it  for  more  than  a  year,  at  the  most  fearful  risk,  until 
public  indignation  became  so  strong  that  a  special  town- 
meeting  was  called,  and  a  committee  appointed  to  remove 
the  old  bridge  and  to  build  a  new  one.    This  is  only  one  of 


V 


many  cases  just  as  bad  which  happen  to  be  within    the 
writer's  knowledge. 

The  Ashtabula  bridge,  it  is  stated  in  the  Ohio  report  above 
referred  to,  had  factors — we  can  hardly  call  them  factors  of 
safety— in  some  parts  as  low  as  1  ^  and  1  ^q,  such  factors 
referring  to  breaking  weight ;  and  even  these  factors  were  ob- 
tained by  assuming  the  load  as  at  rest,  and  making  no  allow- 
ance for  the  jar  and  shock  from  a  railway  train  in  motion. 
Well  may  the  commissioners  saj"  as  they  do  at  the  end  of 
their  report  :  "  The  bridge  was  liable  to  go  down  at  any 
time  during  the  last  ten  or  eleven  years,  under  the  loads  that 
might  at  any  time  be  brought  upon  it  in  the  ordinary  course 
of  the  company's  business,  and  it  is  most  remarkable  that  it 
did  not  sooner  occur." 

One  point  always  brought  forth  when  an  iron  bridge 
breaks  down,  is  the  supposed  deterioration  of  iron  under  re- 
peated straining,  and  we  are  gravely  told  that  after  a  while 
all  iron  loses  its  fibre  and  becomes  crystalline.  This  is  one  of 
the  **  mysteries  "  which  some  persons  conjure  up  at  tolerably 
regular  intervals  to  cover  their  ignorance.  It  is  perfectly 
well  known  by  engineers  the  world  over,  that  with  good  iron 
properly  used,  nothing  of  the  kind  ever  takes  place.  This 
matter  used  to  be  a  favorite  bone  of  contention  among  engi- 
neers, but  it  has  long  since  been  laid  upon  the  shelf. 
No  engineer  at  the  present  day  ever  thinks  of  it.  We 
have  only  to  allow  the  projjer  margin  for  safety,  as 
our  first-class  builders  all  do,  and  this  antiquated 
obj?ction  at  once  vanishes.  The  examples  of  the  long  dura- 
tion of  iron  in  large  bridges  are  numerous  and  conclusive. 
The  Niagara  Falls  railroad  suspension  bridge  was  carefully 
inspected  after  22  years  of  continued  use  under  frequent  and 
heavy  trains,  and  not  only  was  it  impossible  to  detect  by  the 
severest  tests  any  deterioration  of  the  wire  in  the  cables, 
but  ft  piece  of  it  being  thrown  upon  the  floor  curled  up  show- 
ing the  old  "  kink  "  which  the  iron  had  when  made.  The 
Menai  suspension  bridge,  in  which  1,000  tons  of  iron  have 
hung  suspended  across  an  opening  of  nearly  600  ft.  for  55 
years,  shows  no  depreciation  that  the  most  rigid  inspection 
could  detect.  Ii-on  rods  recently  taken  from  an  old  wooden 
bridge  after  60  years  of  use  have  been  carefully  tested,  and 
found  to  have  lost  nothing  either  of  the  original  breaking 
strength  or  of  the  original  elasticity. 

The  question  is  frequently  asked,  does  not  extreme  cold 
weaken  iron  bridges.    To  this  it  may  be  replied  that  no  iron 


so 


bridge  made  by  a  reliable  company  has  ever  shown  the 
slightest  indication  of  any  thing  of  the  Idnd,  though  they 
have  been  used  for  many  years  in  Russia,  Norway,  Sweden 
and  Canada;  and  nothing  that  we  know  in  regard  to  iron 
gives  us  any  reason  to  suppose  that  anything  of  the  kind 
ever  will  happen.    But  here  again  the  whole  question  turns 
npon  the  quality  of  the  iron.    Iron  containing  phosphorus  is 
•'  cold  short,"  or  brittle,  when  cold,  and  will  break  quicker 
under  repeated  and  sudden  shocks  in  cold  weather  than 
when  it  is  warm.    It  is  a  well-known  fact  that  a  good  many 
more  rails  break  upon  New  England  railroads  in  winter  than 
in  sunmier.    In  Scandinavia  this  is  not  the  case,  simply  be- 
cause the  iron  used  in  that  country  is  of  the  bpst  quality. 
In  the  words  of  Mr.  Sandberg,  the  great  Swedish  authority 
on  iron,  "  Rails  made  of  suitable  iron  with  a  proper  section 
will  not  break  in  winter.    In  Scandinavia,   with  a  clhnate 
more  severe  than  in  America,  no  accident  has  occurred  from 
broken  rails.    But  a  very  small  part  of  the  rails  shipped  to 
America  \^'ill  stand  the  proper  test*.    Iron  highly  impreg- 
nated with  phosphorus,  or  cold-short  iron,  is  utterly  unfit  for 
railroad  purposes  in  countries  subject  to  great  and  sudden 
changes  of  temperature."    An  immense  number  of  experi- 
ments upon  all  sorts  of  iron  show  conclusively  that  cold  has 
no  effect  whatever  upon  the  strength  of  good  iron.    The  se- 
curing such  iron  is  a  matter  to  which  the  utmost  attention  is 
paid  by  our  first-class  bridge-building  firms;  but  it  is  a  mat- 
ter to  which  no  attention  is  paid  by  the  builders  of  cheap 
bridges.    We  might  suppose  that  a  person  in  putting  an  in 
sufficient  amount  of  iron  into  a  bridge  would  be  careful  to 
get  the  best  quality;  but  exactly  the  reverse  seems  to  be  the 
case;  on  the  ground,  perhaps,  that  the  less  of  a  bad  thing  we 
have  the  better. 

Many  railroad  companies  in  building  wooden  bridges  take 
no  pains  to  get  iron  rods  which  are  suitable  for  such  work, 
but  purchase  what  is  easiest  to  be  had  in  the  market,  and  in 
many  cases  never  find  that  the  iron  was  bad  until  a  bridge 
tumbles  down.  There  are,' without  the  slightest  question, 
hundreds  of  bridges  now  in  use  in  this  country,  which  as  far 
as  mere  proportions  and  dimensions  go  would  appear  to  be 
entirely  safe,  but  which  on  account  of  the  quality  of  the 
iron  with  which  they  are  made  are  entirely  unsafe;  and 
there  always  will  be  as  long  as  railway  presidents,  superin- 
tendents or  roadmasters  buy  iron  which  they  know  nothing 
about,  to  put  into  bridges.    When  a  bridge  is  finished  the 


81 

ordinary  examinations  never  detect  the  quality  of  the  iron; 
so  that  the  wise  remarks  of  many  inspectors,  or  the  opinions 
of  the  ordinary  hands  employed  on  a  road,  as  to  the  exact 
condition  of  a  bridge  are  of  little  or  no  value. 

We  often  hear  iron  bridges  condemned,  while  wooden 
ones,  so  called,  are  supposed  to  be  free  from  defects.  It 
does  not  seem  to  occur  to  persons  holding  such  ideas  that 
wooden  bridges  rely  just  as  much  upon  the  strength  of  the 
iron  rods  that  tie  the  timbers  together  as  upon  the  timber,, 
and  that  the  effect  of  cold  is  if  anything  worse  upon  the 
iron  rods  in  a  wooden  bridge  than  upon  the  rods  in 
an  iron  bridge,  as  in  the  latter  all  parts  expand  and 
contract  together,  while  in  the  former  the  rods 
and  the  timbers  are  affected  very  differently.  From 
this  cause  it  often  happens  that  the  rods  in  wooden 
bridges  in  the  northern  part  of  the  United  States,  where 
the  temperatnre  varies  from  30  degrees  below  zero  to  90 
above,  by  contracting  bring  upon  themselves  a  strain  enor- 
mously greater  than  they  were  ever  intended  to  bear.  As  a 
matter  of  fact,  where  one  iron  bridge  fails,  a  dozen  wooden 
ones  do  the  same  thing.  One  very  decided  advantage  which 
an  iron  bridge  has  over  a  wooden  one  is  that  we  can  make 
sure  of  good  iron  in  the  beginning,  and  that  we  can  also  be 
sure  that  it  does  not  decay ;  while,  however  good  our  timber 
may  be  in  the  beginning,  we  can  never  be  entirely  sure  of 
its  condition  afterward.  There  are  wooden  bridges  now 
standing  m  this  country  all  the  way  from  50  to  70  years  old, 
which  are  apparently  as  good  as  ever,  while  there  ure  others 
not  10  years  old  which  are  so  rotten  as  to  be  unfit  for  use. 
Especially  difficult  is  it  to  detect  that  most  insidious  foe  to 
timber,  dry  rot,  which,  lurking  in  the  most  inaccessible 
places,  often  eludes  the  most  faithful  examination.  It  will 
not  do  to  assume  that,  because  no  defects  are  very  evident  in 
a  wooden  bridge,  therefore  it  has  none.  When  a  wooden 
bridge,  originally  made  of  only  fair  material,  has  been 
in  use  under  railroad  trains  fol*  S5  or  30  years, 
and  in  a  position  where  timber  would  naturally 
decay,  we  are  bound  to  suspect  that  bridge.  To 
assume  such  a  bridge  to  be  all  right  imtil  we  can  prove 
it  to  be  all  wrong,  is  not  safe.  To  assume  a  bridge  to  be  all 
wrong  until  we  can  prove  it  to  be  all  right  is  a  safe  method, 
though  not  a  popular  one.  Any  person  who  has  had  oc- 
casion to  remove  old  wooden  bridges  will  recall  how  often 
they  look  very  much  worse  than  was  anticipated. 


r« 


fl-'f 


btli 


There  is  one  defect  in  railway  bridges  which  has  often  led 
to  the  most  fearful  disasters,  and  which,  without  the  slightest 
question,  can  be  almost  entirely,  if  not  entirely,  removed, 
and  at  a  moderate  cost.  At  least  half  the  most  disastrous 
failures  of  railroad  bridges  in  the  United  States  have  been 
due  to  a  defective  system  of  flooring.  With  a  very  laige 
number  of  our  bridges  the  failure  of  a  rail,  the  breaking  of 
an  axle,  or  anything  which  shall  throw  the  train  from  the 
track,  is  almost  sure  to  be  followed  by  the  breaking  down  of 
the  bridge.  This  was  without  question  the  cause  of  the  re- 
cent disaster  at  St.  Charles.  A  truck  near  the  middle  of  a 
train  of  17  loaded  stock  cars  broke  down,  so  that  the  car  left 
the  track,  cut  through  the  floor,  destroyed  the  lat<rral  brac- 
ing and  dragged  the  trusses  down  on  top  of  it.  With  the  ex- 
ception of  the  floor  this  was  one  of  the  finest  bridges  in  the 
United  States,  and  was  built  by  one  of  our  very  best  bridge- 
building  firms.  This  was  one  of  four  railway  bridges 
destroyed  from  the  same  cause,  derailment,  in  the  single 
month  of  November  last.  The  report  of  the  American 
Society  of  Civil  Engineers  referred  to  on  a  preceding  page 
observes  in  regard  to  this  matter : 

"  In  most  of  our  railroad  bridges  the  floor  system  is  the 
weak  ix)int.  The  cross-ties  are  short,  the  stringers  are  pro- 
portioned for  a  train  on  and  not  off  the  rails,  and  the  guard 
timbers  are  too  low  and  insufliciently  bolted.  A  derailed  en- 
gine on  such  a  floor  as  this  plunges  CS  the  ends  of  the  cross- 
ties,  into  the  open  space  between  the  stringers  and  the  chords, 
and  generally  wrecks  the  bridge.  To  ob^te  this,  all  cross- 
ties  should  extend  from  truss  to  truss,  and  be  placwl  so  close 
to  each  other  that,  if  sui)ported  at  the  proper  intervals  it 
will  be  impossible  for  a  derailed  engine  to  cut  through  them; 
and  the  stiingers  should  be  so  spaced  as  to  give  them  this 
support.  Next,  the  guard  timbers  should  not  be  less  than 
9x10  inches,  and  should  be  strongly  bolted  or  spiked  to  each 
alternate  cross- tie;  and  lastly,  the  clear  width  between  the 
trusses  should  be  so  great  that  the  wheels  of  a  deraile<l  train 
will  be  arrested  by  the  guard  rail  before  the  side  of  the  wid- 
est car  can  strike  the  truss. " 

Another  point,  which  has  often  been  neglected  is  making 
sufficient  i)rovision  to  resist  the  force  of  the  wind.  A  tornado 
such  as  is  not  uncommon  in  this  countr>',  will  exert  a  force 
of  40  lbs.  per  square  foot,  which  upon  the  side  of  a  wooden 
bridge,  say  of  900  ft.  span  and  25  ft.  high,  and  boarded  up 
as  many  bridges  are,  would  amount  to  a  lateral  thrust  of  no 
jess  than  100  tons;  and  this  weight  would  be  applied  in  the 
worst  possible  manner,  i.  «•.,  in  a  series  of  shocks.  There 
have  been  many  cases  in  this  country  where    bridges  have 


\ 


28 

4)een  blown  down,  and  a  case  recently  came  to  the  writer's 
notice  where  an  iron  railroad  bridge  of  180  ft  span  and  30 
ft.  high,  of  the  Whipple  pattern,  and  presenting  apparently 
almost  no  surface  to  the  wind,  was  blown  so  much  out  of 
line  that  the  track  ha<?  to  be  moved.  No  doubt  the  recent 
terrible  disaster  at  the  Frith  of  Tay  was  due  to  this  cause. 

At  the  time  of  the  Tariflfville  catastrophe  it  was  gravely 
stated  at  the  coroner's  inquest,  and  by  railroad  officers  who 
claimed  to  know  about  such  things,   that  the  disaster  was 
caused  by  the  tremendous  weight  of  two  locomotives  which 
were  coupled  together,  and  it  was  stated  that  one  engine 
would  have  passed  in  safety;  and  directly  afterward  the 
superintendent  of  a  prominent  railroad  in  New  England  is- 
sued an   order  forbidding  two  engines  connected  to  pass 
over  any  iron  bridges.    It  is  all  very  well  for  a  company  to 
issue  such  an  order  so  far  as  it  may  give  the  public  to  under- 
stand   that    it    is    determined    to    use    every   precaution 
Against  disaster,  but  such  an  order  may  have  the  effect  of 
<;i-eating  a  distrust  which  really  ought  not  to  exist.    If  a  rail 
road  bridge  is  not  entirely  safe  for  two  engines,  it  is  certain- 
ly entirely  unsafe  for  one  engine  and  the  train  following, 
the  only  saving  in  weight  by  taking  off  one  engine  being  the 
difference  lietween  the  weight  of  that  engine  and  the  weight 
of  the  cars  that  would  occupy  the  same  room.  For  example, 
a  bridge  of  200  ft.  span  will  weigh  1,500  lbs.  per  lineal  foot. 
An  engine  with  its  tender  will  weigh  60  tons  in  a  length  of 
60  ft.,  and  a  loaded  freight  train  may  easily  weigh  two- 
thirds  of  a  ton  per  lineal  foot.    The  total  weight  of  the  span, 
with  two  engines  and  the  rest  of  the  bridge  covered  with 
loaded  freight  cars,  would  therefore  be  320  tons.    If  we 
take  off  one  engine  and  fill  its  place  with  cars,  we  take  off 
60  tons  and  put  in  its  place  33  tons; ».  e.,  we  remove  27  tons, 
or  just  about  one-twelfth  of  the  working  hmd.    Taking  off  a 
large  part  of  the  working  load,  however,  is  taking  off  a  very 
small  part  of  the  breaking  load.     With  a  factor  of  safety  of 
six,  for  example,  taking  off  one-twelfth  of  the  working  load 
is  taking  off  less  than  one-seventieth  of  the  breaking  load. 
An  order,  therefore,  like  that  above  can  only  be  of  use  when 
fhe  working  load  and  the  breaking  load  are  so  near  alike 
that  the  actual  load  is  a  dangerous  one  ;  that  is,  when  the 
bridge  is  unfit  for  any  traffic  whatever;  so  that  if  such  an 
order  was  reaUy  needed,  it  would  in  itself  be  in  the  eyes  of 
an  engineer  a  condemnation  of  the  bridge. 
Having  seen  something  of  the  structures  which  require  in- 


\ 


r-j. 


t 


specting,  let  us  now  see  whnf  ti^^  ^#  • 

this  country,  and  thrriS^l '^fi  "'^nT'""  ?  """ '" 
inspection  which  we  m.Vhf  h!         ^         let  u»  uJk,  see  the 

be  produced     2>o4Tfl^t  ^^^7^^"  "^"^  "»'  "^"t 
suppled  that  n^Sd^so^Sr^  ^T"' •  "* 
such  structures  in  good  orrlAr     "'"'""'"*'«<*«  in  Iceeping 
those  bridges,  and  ll^t^Z  Z  SLT**'""  ""'"'  ""■' 
«*er.    This  is  of  .v,,/.!         u  *"  ""^  '" "»««  »'  ("is- 

over  half  anUllion  doZ^N^ittdTT"^  """'"""« 
down  which  the  owners  wL  "°  ™''^'«<»  ''"'•ge  ever  broke 

but  there  is^^:^^TZZtTT^'"'"^'"''^'^''' 
Penses  unU,  the  Lt  moZnt,  auTthl  S'* '"^''  "'" 

a  ie^siativf  — SI  •tTnrr  o/'l^  ^^^ 
roads      were       not      safe      tn      .T  ^°'*^^®'* 

such  roads  w.>r«Ko-         .  '^"^      ^^^'■'      but     that 

keep  ^i^  ;^t  Z^  "  ^'■™«-  r  ™""'  "•"  '"'°"'  to 
the  past  ten  7«r."ter?Xi;!^??.r '"'"'"■  ^•^'^ 
States  have  broken  dowl     t^  ^"^  ''"'^  *»  the  United 

suchinspectionLthtmUnl       ''""^"^"■'"'^P'""''" 

the  supervision  t^dXtiveofth?"  "^"""^  ''"*"'^«' 
continued  the  use  of  ^XZZ^tT^::.TT<''y 
means  been  confined  f^  thJ      ^  '*"^^  ***«  ^X  »<> 

would  seem,reX^t.lT  .Wwr^nr  "^"^  '* 
themselves  has  not  bee;  suffleienT^u^^^„^t  ~""*''**» 
enough  t»  prevent  ion  T   !        " '*tau''y  has  not  been 

cust^^inse^eXU^U^'^^sl^Lf""*^-  ""  "« 
termed  a  railroad  comm,L"r^  ?^.  T""*""  '"»'  '» 

to  have  been  for  f ^  ^^     "^"''  '"tention  seems 

under  som^ld"fX«r^°"  "^  """•  ^^^  "•"-<». 
settling  the  vario^  C"s' rhlL"  Z LT- *"  ^^^  *" 
different  railroad  companir  I„H    .  7*  "   '*'"**° 

paniesandthepub^  uZ'theUt.  °*°  railroad  com 
quickly  dismiss'  a^\u^J,  Jft  "Z**  "^'^ '^^.  """^ 
organi^tions.    It  is  Ir.^/ uT^VX^^'Z^^Zr 

^h^TLs^lTtbT  •*""''  ""■  ""«»« 

questions  "  'a  Z^^Z  "Z  i"*^,*""  «»^««f1 
Pointees.  Even  in'trcTusett'^whrro  ?^e'"*',  '^ 
commission  app^„ini,,  best  aspect.  rtt':i^tUtTtf 


25 

strongest  advocates,  after  ten  years  of  existence,  to  be  but 
■an  experiment  which  cannot  yet  be  pronounced  an  assured 
success.  With  regard  to  the  value  of  the  inspection  of 
bridges,  by  any  such  commissions,  we  should  hardly  suppose 
that  three  men,  in  many  cases  entirely  unacquainted  with 
mechanical  matters,  could  by  riding  over  a  railroad  once  or 
twice  a  year,  occasionally  getting  out  to  examine  the  paint 
on  the  outside  of  the  boards  which  conceal  a  truss  from 
view,  judge  very  correctly  of  the  elastic  limit  of  the  iron 
which  they  have  never  seen,  and  of  which  they  do  not  even 
know  the  existence. 

For  ample  proof  of  the  utter  inefficiency  of  the  present 
system  of  public  inspection,  we  have  only  to  compare  the 
reports  of  the  railroad  commissioners  in  almost  any  state 
with  the  actual  condition  of  the  structures  described.    The 
writer  has  done  this  to  a  certain  extent  in  several  states,  in 
which  he  has  now  a  personal  knowledge  of  many  bridges.    In 
one  state  the  last  annual  report  covers  a  whole  railroad  witE 
the  remark,  "  All  of  the  bridges  on  this  line  are  in  excellent 
order ; "  and  yet  there  were  at  that  very  time,  and  ai-e  now,  on 
that  road,  several  large  wooden  bridges  with  a  factor  of  safety, 
referred  to  the  breaking  weight,  of  not  over  two,  under  a  fair 
load,  assuming  the  iron  rods  to  be  of  the  very  best  material,  a 
point  upon  which  the'-e  is  no  evidence  whatever.    In  another 
state  an  iron  bridge  is  in  use  under  heavy  trains  which  has  a 
factor  of  only  two  and  a  half,  and  yet  the  state  report  pro- 
nounces it  an  excellent  structure  and  a  credit  to  the  railroad 
company  (which  furnished  the  commission  with  free  passes). 
In  a  third  case  the  commissioners  stated  plainly  to  the  writer 
that  a  certain  bridge  was  undoubtedly  weak,  but  that  it  was 
on  a  line  over  which  very  few  passengers  traveled.    A  man's 
neck,  however,  is  as  valuable,  as  far  as  the  owner  is  con- 
cerned, oti  one  road  as  on  another.     In  one  instance,  in  an- 
swer to  the  enquiry  how  the  coromiFsioners  had  been  able  to 
report  upon  a  large  wooden  bridge,  which  was  so  covered 
in  as  to  be  entirely  hidden,  it  was  replied  :    '•  Well,  we  went 
over  that  bridge  in  the  night ;  but  the  road-master  told  us 
that  the  bridge  was  in  good  order."     No  wonder  that  rail- 
road officials  have  an  undisguised  contempt  for  the  state  in- 
spection.     The  commissioners  of  three  of  the  most  import- 
ant states  in  the  Union  did  not  hesitate  to  admit  to  the  writ- 
er a  year  ago  that  no  one  of  them  had  ever  computed  the 
strains  on  a  single  bridge  in  the  state,  but  supposed  that  to 
be  the  business  of  the  builder  ;  and  one  ofiicer,  in  reply  to  a 


i) 


iMnMll 


\ 


■such  in^peotion^tLt irr  "retlSr"^  r^htrr'^ 
T^iffvnie  bridges,  fe„  and  kuJS^veTir^t  e  "^ 

WhUe  m  a  ew  »tate,  the  inspection  is  not^r^.  bad  .. 

bHdg^dJi:';^,r;r,»^r:''"™"'*'"'^"^'"«»'^«> 

-o^'tiJ'C  !:  lif '""^  ''"'^'  "«  ■«•  «  Po-iWe,  even 

be     less     than     800.      This   is  about  nn  '^''°* 

every  two  states,  and  is  no  d:ubt  J^withT:  th'   IZ.  '7, 

bnd.e-bui.aerrthr^„r.,*:„rsr"  '•^-  '"^-- 

gard  to  bridges  or  bridge-builders     In  J3?     .        ""  "^ 
from  some  one  conveiSit  «-^h       '°^^«»  of  gettmgadvice 

themselves  to  belm^  l"  „  k    .k  "'"*'*''''  *"">'  »"°»«^ 

they  knewnotWngaC^  Tbn^d^"  '*^"'  "'  *  '*°«'"' 

to  make  its  own  tcwlioI'^.^T.irTthTL^Z:' 

^oLrr;::rar::-':-rTr^^^ 


t 


87 

price,  and  gave  the  town  a  bridge  which  a  committee  of 
experts  reportetl  had  a  factor  of  safety  of  1  15-lOOths,  and 
would  cei-tainl y  fall  under  a  heavy  load.  Add  to  this  the 
fact  that  the  county  com  nissioners  iu  the  next  town,  in  full 
knowledge  of  all  that  had  been  done  above,  deliberately  pro- 
ceeded to  employ  the  same  company  to  make  another  bridge  of 
exactly  the  same  kind,  and  we  can  see  pretty  clearly  the  value 
of  the  present  system,  if  it  can  be  called  such,  of  highway 
bridge  work  in  this  coimtry ;  and  the  above  is  a  perfectly 
fair  specimen  of  the  general  practice  in  the  United  States. 

If  we  knew  positively  that  in  just  six  months  a  terrible 
disaster  would  occur  under  the  present  system  of  railroad 
inspection,  and  knew  also  that  by  a  better  system  such  dis- 
aster would  certainly  be  prevented,  it  is  possible  that  a 
change  would  be  made.    We  know  that  a  proper  method  of 
building  and  of  inspecting  bridges  would  certainly  have  pre- 
vented the  disasters  at  Ashtabula,  Tariff ville  and  Dixon. 
We  know  that  the  inspection  which  those  bridges  received  ^ 
did  not  prevent  three  of  the  most  fearful  disasters   the 
country  has  ever  seen.    Admitting,  now,  that  structures  so 
important  to  the  public  safety  as  bridges  both  upon  roads 
and  railroads  ought  to  be  kept  under  rigid  inspection  and 
control,  and  that  no  system  at  present  existing  has  been  able 
to  prevent  the  most  fearful  catastrophes,  what  shall  we  do  ? 
Directly  after  the  Ashtabula  disaster  the  Ohio  legislative 
committee  appointed  to  investigate  that  affair  presented  a 
bill,  evidently  suggested  by  the  report  of  the  American  So- 
ciety of  Engineers,  '*To  secure  greater  safety  for  public 
travel  over  bridges,"  in  which  was  plainly  specified  the 
loads   for    which     all     bridges    should     be   proportioned, 
the  maximum  strains  to  which  iron  should  be  subjected, 
and  a  method  for  inspecting  the  plans  of  all  bridges  before 
building  and  the  bridges  themselves  during  and  after  con 
struction.    The  Governor,  with  the  consent  of  the  Senate, 
was  to  appoint  the  inspector  for  a  term  of  five  years,  at  a 
salary  not  exceeding  $3,000  a  year;  such  inspector  to  pass 
a    satisfactory   examination    before   a    Ck>mmittee  of   the 
American  Society  of  Engineers,  themselves  practical  experts 
in  bridge  construction,  and  he  was  also  to  take  a  suitable 
•oath  for  the  faithful  performance  of  his  duty.    This  bill 
never  became  a  law.    An  appropriation  was  made  for  a 
short  time  to  pay  for  certain  examinations,  and  there  the 
matter  stopped. 

The  Committee  of  the  American  Society  of  Engineers 


28 

were    not  agreed  upon    this    matter.     Messrs    James  R 
f:^J:'t2T.  "*^-^^«-^*»^-«^tedthe^p;^„Tm\n,' 

e^'^^'havet:"  ""   "^'^  ^*^^"^^  "^  inspected,   "ct 
expert    to   have   been   examined    and    approv^  bv   thl 

Amencan  Society  of  Engineers.    This  insp^^  ^^  ^L'^ 

vi^t  the  scene  of  every  accident,  so  cai^^^d  Toas^^ 

as  far  as  possible  the  cause.    Messrs.  Thomas  C   Cl^^ 

that  i/^'  .  ^^  °'^**'^  ^^^^  ^  impracticable,  and  fWed 
that  ,f  mspectors  were  appointed,  it  wouJd  be  by  polkic^ 
fluence,  and  that  the  result  would  be  worse  than  at'^^T  t 

ISmv"""^  incaaeoradtaaster  io^tZryZ^ 

paK»f,  snouid  be  the  legal  standard,  and  in  case  ii-  «h«»w  i^ 
^u^d  that  aay  bridge  „aa  o, !«.  ^ngthlbrt^ t  "ho„i^ 
be  taken  as  pnma  /aw  evidence  of  neglect  on  the  n-H^f 

^^  .h.tL  .Cfr3"Lrxr;nrtre3rjrtt 

corporation  having  control  o(  it  had  been  deDcitJT with  ,k 
American  Society,  and  further,  that^^pri^'^p":!'^? 

Tke^^W  "„?*''"'";"'  •«  "tamped  With'  t^e^'^^rthi 
maker,  ptace  of  manufacture  and  date.    Messrs  Alfred  P 

it  tL' H   '"^""  *^""»'"'  '*"'«•  "'therTwa^^ect: 
Wfa^  tt"::?  "T"'- '"'  ™'»«<^«-<f  public  sentimen^y 

»re  to  keep  the  number  of  .ppHca^rdorntat-S 
low  figure.    In  case  such  a  plan  was  found  fearibirk^th! 

^etS^n  e21  '"T-  "^  "'~"  "■"  -^«i"n''of 
Me  oociety  of  Engineers,  as  inspector  of  roads  and  bridirea 
or  state  engineer.     Pay  him  for  his  whole  time  and  iTt  7^' 
give  his  whole  time  to  the  work,  for  he  wiUnt^STdo  ^ 
'»uch  person  should  have  in  his  i««ession  a  co^let^  «?  oi 


\ 


29 

plans  of  every  bridge  of  importance  in  the  state,  with  ail 
the  computations  of  its  strength,  and  as  complete  a  history 
of  each  structure  from  its  commencement  as  can  ixjssibly 
be  made  up,  all  this  to  be  supplemented  by  at  least  tw©  annual 
examinations.  If  from  such  records  we  find  that  a  bridge 
was  made  of  ordinary  green  timber,  25  years  ago,  and  that 
it  has  been  getting  rotten  ever  since,  that  it  has  rods  of  com- 
mon merchant-iron  that  were  bought  by  the  president  or 
superintendent  of  a  railroad  from  an  unknown  firm,  we 
had  better  pull  it  down  before  it  falls.  If  from  such  records 
we  find  an  iron  bridge,  built  25  years  since  by  an  unknown 
company,  with  iron  at  best  of  doubtful  quality,  and  having 
a  factor  of  three  or  four  for  the  rolling-stock  and  speeds  of 
twenty  years  ago,  instead  of  a  factor  of  six  for  the  rolling- 
stock  and  speeds  of  to-day,  we  had  better  remove  that  bridge 
before  it  removes  itself. 

Such  a  record  would  be  the  property  of  the  state,  always 
accessible  to  any  oqe,  and  would  be  handed  down,  so  that 
the  knowledge  of  one  person  would  not  expire  with  his  term 
of  oflBce.    No  bridge  should  be  erected  in  any  state,  with- 
out first  submitting  the  plans  to  the  inspector,  and  receiving 
his  approval,  and  depositing  with  him  a  complete  set  of  the 
plans  and  computations  for  the  work.    By  this  approval,  is 
not  meant  that  the  inspector  is  merely  to  give  a  favorable 
opinion  as  to  the  plan,  but  that  he  is  to  find,  as  a  matter  of 
fact,  whether  the  proposed  dimensions  and  proportions  are 
such  as  will  make  a  safe  bridge;  and  just  what  a  safe  bridge 
is  can  be  plainly  defined  by  law,  as  it  is  in  Europe,  and  as  it 
has  been  proposed  by  the  American  Society  of  Civil  Engi- 
neers. ^  For  example,  if  the  law  says  that  an  iron  railway 
bridge  of  100  feet  span  shall  be  proportioned  to  carry  a  loaa 
of  3,000  lbs.  per  lineal  foot,  besides  its  own  weight;  and  that 
with  such  a  load  no  part  shall  be  strained  by  more  than  10,- 
000  ibs.  per  inch;  all  the  inspector  has  to  do  is  to  go  over  the 
figures  and  see  if  the  given  dimensions  on  the  plan  are  such 
as  will  enable  the  bridge  to  cany  the  load  without  exceeding 
the  specified  strains.    When  the  work  is  erected,  the  inspec- 
tion must  know  that  the  plan  has  been  exactly  carried  out, 
and  good  evidence  of  the  quality  of  the  material  used  should 
also   be   given.    Such   inspection    as  this    would  at   once 
prevent  the  erection  of  bridges  like  those  at  Ashtabula  and 
Tariflfville,  and  would  save  the  public  from  such  traps  as 
that  at  Dixon,  and  the  one  at)ove  referred  to  as  having  a 
factor  of  safety  of  l^^o 


80 

or  eont.0.  .t  p^„t  exiSnX  b^^  S^"  ^JtTtT 
van^  the  defect  in  the«,  ,tr„ctu„«.  or  to  p^^rthe  i^" 

ne  tad,  which  If  properly  carried  out  will  insure  in  nearir 

ac  Z:;  wh"!"^'-  "^  -•"•"<=  »""^-    »  ««  with  theT^ 
Uc  to  say  whether  or  not  it  will  have  such  a  system. 


\ 


tl'"'^''' 


^ 


BAILED  AD  (JAZETTE_PUBLIOATIONS. 

Th«  R,ilro«,  Ou,tt,,nBro,aw^,  N.w  York. 

Specimen  copiig  fJw      iI;»«h    ™  America.    J4.'J0 per  year. 

BOOKS 

r"-®^-     ffl-V^""  '^""■'»'  "-'«^'-    By  A.  M.  W.U. 
BaUway  ReyeSue  anditrcv3te?,S^SiS''«'e''i. ,  Wee,  $l.-,a 

!;'fe¥;:J^=  '^"  ""^  S^""      B,   M.   M.    Kirkmao. 
Friction  and  Lubrication     Bv  1i  h  tu^-^         *_, 
Car-Builders'  Dlctionwr      fiv  a  «.S?^"-  ,P^<»Jl.-'iO. 
.    Builders'  A«»ciatlon      WK)  «^^'?"'^  **'«'*»«  *»a«ter  Car- 
^  bertWndinTI^.?"  *^  ^^"^n^^'^g^-      Price,   |a.oo.    in 

p«-*«*,>.  PAMPHLETS. 

t;Ort  Of  PasBen«rer  Traffic  (Tink) 

Cost  of  RjOlroad  TriSspotiiffi  Vpin^^^^ tO.75 

S?  ^SS?L^te^^«l^.p:::::;:.:.:;.;;  •:  8:Je 

Locomotives  for  Rapid  Transit  (Fonevl ^'*^ 

Stan^  and  Narrow  Gau|re%mi  wili:;; ^.40 

Description  of  the  Billeri«!&  BeAor^^^  n.   • ' *  »  'A' ^.25 

Taxation   of  RailPoSB  knd  p^n^-^  o     ®?H«*  ^- ^ 0.25 

Adams,  Jr.,  W\B^u£S?8  J^S^  S^  ^y  C  F. 

American  Raaway  ^^ter  ^^.^^^1^,1^^- j^^^;^  0.20 

Master c«-Buiiders'Aw;x:iationR^rtk;each:.::. ;:;:;::::  ^^^ 


JSiSNiBSiiS' 


jm.-'^-s.  9  ^  n 


H 


GAYLAMOUNT 
PAMPHUT  MNDEIt 


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